This invention relates to suspension systems and, more particularly, to suspension systems which include suspension struts.
In the typical MacPherson strut commonly found on many passenger vehicles, a hydraulically damped strut and a coil spring respectively provide damping and load bearing support for the vehicle. As a front-end suspension, an endless bearing acts between the top mount and the upper end of the spring to permit rotative movement between the cylinder and the piston rod of the strut in response to turning effort applied to the cylinder via the bottom mount during turns. Due to this location of the bearing, however, rotative shifting of the cylinder is subject to a mechanical disadvantage related to the diameter differential between the bearing and the cylinder. Turning effort required to rotate the cylinder with respect to the spring and piston rod during turns therefore must be sufficient to overcome this mechanical disadvantage. Even more turning effort is needed if the frictional resistance to such rotation is increased on account of the presence of dirt or other material at the rotational interfaces between the cylinder and piston rod. As more and more rotational effort is thus required, of course, the ride and handling properties of the suspension become less and less predictable, or even unsatisfactory.
Tubular elastomeric springs have certain advantages, in some suspension applications, over coil springs. It accordingly is desirable in such applications to substitute tubular elastomeric springs for coil springs. In the case of the strut suspensions of the type just described, however, this is not always practical. The spring seats commonly used to support coil springs generally are of an irregular configuration which conforms to the contours of the end coils of the springs involved. Unlike coil springs, tubular elastomeric springs operate more effectively when supported between continuous annular spring seats, especially if it is desired to establish a seal at the ends of the spring for purposes of dirt prevention and/or internal pressurization. In addition, the endless bearings commonly used with most top mounts to permit relative rotative movement between the cylinder and piston rod often provide unsatisfactory protection against the entrance of contaminants and moisture.